Mattis will be joined by Air Force Gen. Paul Selva, vice chairman of the Joint Chiefs of Staff, at a hearing of the House Armed Services Committee focused on the Nuclear Posture Review (NPR), outlined last Friday at the Pentagon, and the National Defense Strategy (NDS), which unveiled last month.

The review sought to back up Mattis on how the U.S. nuclear deterrent would be channeled in confronting Russia and China, which are now viewed under the strategy as the main security challenges to the U.S., replacing terrorism.

Over the weekend, both Russia and China labeled the review as a misguided Cold War relic that would only encourage nuclear weapons proliferation.

In a statement, China's Defense Ministry said its own nuclear arsenal was at the "minimum level" required for its security and called on the U.S. to "abandon a Cold War mentality" and "shoulder its special and prior responsibility for its own nuclear disarmament."

Russia's Foreign Ministry characterized the review as both "confrontational" and "anti-Russian." The Russian statement went on to call the document "an unscrupulous attempt to shift onto others one's own responsibility for the degrading situation in the field of international and regional security."

For its part, North Korea was planning a massive military parade just before the Winter Olympics begin on Feb 8 at which its intercontinental ballistic missiles, or ICBMs, were expected to be on display, including the Hwasong-14, first tested last July, and the heavier Hwasong-15, tested in November.

The Nuclear Posture Review outlined "tailored strategies" for dealing with Russia, China, Iran and North Korea, while also calling for the development of a new "low yield" submarine-launched ballistic missile and a new sub-launched cruise missile.

The U.S. has never completely ruled out the "first use" of nuclear weapons, but the review went further and said the country would consider a nuclear first-strike response under the "extreme circumstances" of a devastating conventional attack.

The "tailored strategy" for Russia was intended to "pose insurmountable difficulties to any Russian strategy of aggression against the United States, its allies, or partners and ensure the credible prospect of unacceptably dire costs to the Russian leadership if it were to choose aggression," the document said.

"Our tailored strategy for China is designed to prevent Beijing from mistakenly concluding that it could secure an advantage through the limited use of its theater nuclear capabilities or that any use of nuclear weapons, however limited, is acceptable," it said.

"For North Korea, the survival of the Kim [Jong-un] regime is paramount. Our deterrence strategy for North Korea makes clear that any North Korean nuclear attack against the United States or its allies and partners is unacceptable and will result in the end of that regime," the document said.

On Iran, the review said the main goal was to prevent Tehran from developing nuclear weapons. "Were Iran to decide to acquire nuclear weapons, pressures on other countries in the region to acquire their own nuclear weapons would increase," it said.

At the House hearing Tuesday, Mattis and Selva were also expected to be pressed on the overall costs of the review. Pentagon officials last Friday declined to give a cost estimate while stating that it would be a small percentage of the overall budget

However, the nonpartisan Congressional Budget Office has put the cost of modernizing the nuclear triad of bombers, land-based missiles and submarines through 2040 at $1.2 trillion.